Block chain

Block chain definition: blockchain is a ledger of facts, replicated across several computers assembled in a peer-to-peer network. Facts can be anything from monetary transactions to content signature. Members of the network are anonymous individuals called nodes. All communication inside the network takes advantage of cryptography to securely identify the sender and the receiver. When a node wants to add a fact to the ledger, a consensus forms in the network to determine where this fact should appear in the ledger; this consensus is called a block.

The technology behind the blockchain uses advanced cryptography, custom network protocols, and performance optimizations. This is all too sophisticated to be redeveloped each time a project needs a blockchain. Fortunately, aside of Bitcoin, there are several open-source blockchain implementations. Here are the most advanced:

Ethereum: an open-source blockchain platform by the Ethereum Foundation

Eris Industries: Tools helping to manipulate Ethereum, Bitcoin or totally independent blockchains, mostly to build private networks. Their tutorials and explainers are a great starting point for an overview of the blockchain technology.